Prenatal DES exposure may not affect male fertility

NEW YORK (Reuters Health) - Men exposed to the drug diethylstilbestrol (DES) before birth appear not to have reduced fertility or be less likely to father boys, researchers have found.

DES, a synthetic form of estrogen, was introduced in 1941 as a drug that prevented miscarriage. An estimated 2.4 million US women took the drug before its use during pregnancy was banned in 1971.

The drug appears to cause structural changes in the reproductive organs of both female and male children exposed to DES before birth.

"There have been conflicting research results through the years regarding whether DES sons have higher infertility rates than unexposed males," Dr. Lauren A. Wise, lead author of the new study, told Reuters Health.

To investigate further, Wise of Boston University and colleagues examined data from 1,246 DES-exposed and 1,250 unexposed men participating in the National Cancer Institute DES Follow-up Study.

The investigators studied time to pregnancy -- the number of menstrual cycles from the time a couple stops contraception until a pregnancy is achieved -- and they also explored any differences in offspring sex ratio between the exposure groups.

The findings, Wise said, "showed that DES-exposed men were able to father children at similar rates to those for unexposed men, and while DES-exposed men fathered fewer boys than unexposed men, the difference did not reach statistical significance."

These results suggest that exposure to DES in the womb "does not adversely affect fertility rates in men or does it appear to affect the sex ratio of their offspring."

"These results provide some reassurance that exposure to DES in utero does not appreciably affect male fertility," she concluded.

SOURCE: American Journal of Epidemiology, October 1, 2007.